Apparatus and method for forming a terminal

ABSTRACT

The invention relates to apparatus and methods for forming a terminal on a battery. Terminal forming apparatus ( 11 ) has a mould ( 12 ) with a cavity ( 26 ) which is intended to encircle the post and bush assembly ( 22, 25 ) of a battery box ( 10 ). The mould cavity ( 26 ) is formed with an open upper mouth ( 27 ) and a lateral inlet/outlet ( 28 ) which connects with the feed channel ( 13 ). Inlet ( 28 ) is defined by a weir ( 29 ) which acts as a constant height device to define the final filling height of the mould cavity ( 26 ). This arrangement allows over filling of the mould above the height of the weir ( 29 ) and subsequent dropping of that level to the height of the weir ( 29 ). This enables the terminal to be formed at precisely the correct height without the need for any metering of the lead.

This invention relates to apparatus and methods for forming a terminalon a battery and in particular, but not exclusively, a terminal on thebattery of the type having a battery box, containing groups of batteryplates, which are interconnected by respective straps to respectiveposts which connect to the positive or negative terminal respectively.

Currently the procedure is to locate and secure the battery lid to thebattery box such that the posts pass through a respective aperture inthe lid. The aperture is defined by a bush, which may either besubstantially flush with the lid or may extend above the lid to the fullterminal height. To some extent the bush size is a matter ofmanufacturing choice, but where high currents have to be drawn, e.g. fordiesel engine truck batteries, the terminal height bush is oftenunsatisfactory, because, in order to assist lead in, the interior holeis essentially frustroconical and the connection formed between the postand the connection formed between the post and the terminal often is ofonly a small depth. The connection between the post and the bush isformed by fusing the post to the bush, for example by using a heatedprobe, which is pressed down onto the free ends of the post and bush. Itis difficult to form a satisfactory upper surface.

Where the bush is substantially flush with the lid, current procedure isto fuse the post and bush, again by heated probe, and then to mould aterminal on top of the post/bush assembly. Currently the mould is placedupon the assembly and an operative spoons lead into the mould until itis level with the top of the mould cavity. It will be appreciated thatthis is extremely labour intensive and somewhat slow. Attempts have beenmade to automate the process, but it is extremely difficult to delivermetered quantities of liquid lead and the alternative approach offeeding lead wire of known diameter at a metered rate immediately fallsdown, because the cost of forming the wire exceeds the labour cost.

From one aspect the invention consists in apparatus for forming aterminal on a battery, wherein the battery has a lid having a metal bushand a post connecting a group within the battery and located with itsfree end in the bush including:

-   -   (a) a fusing device for fusing the post to the bush to form an        assembly,    -   (b) a mould having a cavity engaging the assembly and for        forming or finishing a terminal        characterised in that the mould cavity extends above the        intended height of the terminal to allow for overfilling of the        mould and the cavity includes a constant height structure to        define the final fill level of the mould.

By overfilling the mould and letting the level fall back to the level ofthe constant height device, the terminal can be formed precisely at thecorrect height, without any metering of the lead having to take place.This approach, and indeed the method set out on page 5, is beneficialwith either type of bush, because in the case of the terminal heightbush, the lead can be utilised to fill in any dimples or recesses leftafter the post/bush fusing step.

The apparatus may include a pump for pumping molten material into thecavity. However the molten material is driven, it may be introduced intothe mould via the constant height structure and, conveniently, theconstant height structure may be in communication with an inlet/outletchannel, which may include a valve for determining the height of themolten material in the inlet/outlet channel relative to the constantheight structure. Thus whilst the valve is open, the lead in the channelmay be kept below the level of the constant height structure, whilstwhen the valve is closed it may rise up above the constant heightstructure and thus fill the mould.

The constant height structure may be a weir and the weir may be inclineddownwardly in the direction of outflow from the cavity.

The apparatus may further include a displacement body for introductioninto the mould cavity to ensure that any excess material flows out ofthe mould.

The fusing device may be a heatable probe for engaging and fusing thepost and bush, in which case the tip of the probe may be formed toengage the tip at the post. For example, where the post isbullet-shaped, the free end of the probe may be recessed to accommodatethe tip of the post. The probe may have a dependent skirt at its tip formelting at least part of the inner periphery of the bush to enhance thequality of the joint formed. The probe may be mounted for movement intoand out of the mould cavity and may constitute the displacement body.

The probe may be heated by at least one gas jet and the apparatus mayinclude a control for increasing the strength of the gas jet when theprobe is remote from the cavity after moulding to surface treat the tipof the terminal and/or to displace any flashings from the terminal.

A part of the mould may include a thermal break adjacent the level ofthe lid of the box to retain heat at the base of the mould.

From another aspect the invention includes a method for forming aterminal on a battery wherein the battery has a lid having a metal bushand a post connected to a group within the battery and located with itsfree end in the bush wherein the post is initially fused to the bush andthe terminal is moulded on the fused bush and post assembly in a mouldencircling the assembly characterised in that the mould is initiallyoverfilled with terminal forming material and subsequently the excessmaterial is allowed to flow out of the mould.

Preferably the post is fused to the bush whilst located in the mould andconveniently the post and bush are fused by engagement by a heated probeintroduced into the cavity of the mould. The probe may be withdrawn fromthe cavity during the filling of the mould and subsequently dipped intothe mould cavity to displace any remaining excess material.

The method further includes playing a jet of hot gas on the surface ofthe terminal, after the excess material has flowed out, to remove anyflashings.

It is preferred that heat is retained in an area of the assembly whilethe terminal solidifies. Thus it is particularly preferred that the heatis retained in a region below the tip of the post so as to ensure thatfusing takes place along the height of the intended joint.

The tip of the terminal may be re-heated as solidification occurs.

Although the invention has been defined above, it is to be understoodthat it includes any inventive combination of the features set out aboveor in the following description.

The invention may be performed in various ways and specific embodimentswill now be described, by way of example, with reference to theaccompanying drawings, in which FIGS. 1 to 5 are schematic side views ofterminal forming apparatus in different stages of the sequence ofoperation.

As can be seen in FIG. 1 a battery box, generally indicated at 10, ispresented adjacent a terminal forming apparatus 11. The terminal formingapparatus 11 includes a mould 12, an inlet/outlet feed 13, a verticallead supply pipe 14, a pump 15, a lead pot 16 and a fusing probeassembly generally indicated at 17.

The battery includes a box 18 having compartments, one of which is shownat 19, that contain groups of battery plates 20 that are interconnectedby straps 21 that are directly or indirectly connected to a respectiveone of a pair of posts, one of which is shown at 22. One post 22 is usedto form the negative terminal of the battery, whilst the other is usedto form the positive terminal. The battery 10 has a lid 23 with anaperture 24, for each post 23, that is defined by a respective bush 25.

As can be seen in the Figures, in use, the battery is presented to theterminal forming apparatus 11 so that the cavity 26 of the mould 12encircles the post and bush assembly 22, 25.

The terminal forming apparatus 11 will now be described in a little moredetail. First it will be seen that the mould cavity 26 is formed with anopen upper mouth 27 and a lateral inlet/outlet 28 which connects withthe feed channel 13. The inlet 28 is defined by a weir 29, which has anupper surface 29 a which is downwardly inclined in the direction of thefeed channel 13. The weir 29 therefore serves to act as a constantheight structure, which defines the final filling height of the mouldcavity 26. A thermal break 13 a exists between the weir 29 and the feed13.

At the other end of the feed channel 13 is a dump valve 30, which isconfigured such that, when it is open (as illustrated in FIG. 1), theheight of lead in the feed channel 13 does not exceed the dotted line31. I.e. it is kept below the level of the weir 29. The feed channel 13is supplied by the pump 15, which is driven by a motor 32. The pump 15drives molten lead from the lead pot 16 up the supply pipe 14 so that itflows into the channel 13.

The probe assembly 17 includes a probe 33 mounted on a head 34 forupward and downward movement, axially, into and out of the mould cavity26. The head has a crown of gas jets, schematically indicated at 35,which are utilised to heat the probe and for other purposes indicatedbelow.

The operating sequence of the apparatus begins with the FIG. 1 positionin which, as has already been described, the mould 12 is located on thebush 25 with the probe raised. The pump 15 is preferably circulating atthis time, but any excess lead delivered to the feed channel 13 returnsto the lead pot 16 via the open dump valve 30. In FIG. 2 the probeassembly 17 is lowered into the mould so that the probe 33 engages themould and bush to fuse the two together. As can be seen in FIG. 1, thetip 33 a of the probe 33 is formed with an axially facing recess 33 b.This has the advantage that it allows the resultant peripheral skirt ofthe tip 33 a to pass down beyond tile upper portion of the post 22 toengage and heat the bush 25 and thus enhance the quality of the jointformed. It will be understood that the shape of the tip 33 can beadapted to accommodate the post and bush structures adopted byparticular battery manufacturers.

In FIG. 3 it can be seen that the post 22 and the bush 24 have beenfused together to form an effective assembly and the probe assembly 17has been raised. The dump valve 30 is now shut and the level of the lead31 rapidly rises above the height of the weir 29 so that lead pours intothe mould cavity 26 to a height, which is above the height of the weir29 and hence the intended height of the terminal. At this point the pump15 can be switched off, as indicated in FIG. 4. The lead level 31 beginsto drop until it is approximately level with the top of the weir 29. Atthis point the probe 33 is once more lowered into the cavity 26 todisplace any excess material within the cavity 26 and the commensuratere-heating of the top of the terminal 37, which is forming in thecooling mould, enhances the surface of that terminal.

Finally, as shown in FIG. 5, the dump valve 30 is once more openedallowing the lead to drop below the level of the weir 29 and completingthe run back of any lead from the cavity. At this point the gas jets 35are significantly turned up so that a jet of flame 35 b shoots into themould 26. The combination of heat and gas flow removes any flashingsthat have been formed around the edge of the terminal and also completesthe surface treatment of the terminal 36.

It will be understood that there will usually be two such mouldingapparatuses 11 so that the posts of the battery 10 can be processedsimultaneously, but alternatively, the battery box could be sequenced onso that the next post can be processed.

Many variations of the apparatus are contemplated. The gas jet heatingcould be replaced by other heating means, for example an inductionheater. The induction heater could be formed on the probe assembly 17 orcould even be located in the mould itself. The displacement body couldbe other than the mould and its function could be replaced purely by theuse of a jet of gas to displace excess material.

In general it is desirable to keep the base of the bush warmer than thetop of the post during the post fusing stage so as to ensure fusingalong the length of the joint. This may be done by providing a thermalbreak. In some instances care may be needed to ensure that the lid 23has not melted and cooling air could be applied externally in thevicinity of the bush 25.

Other methods of supplying lead could be utilised. The system simplyneeds the ability to overflow the weir 29 and then to allow run back oflead out of the mould 26. Thus, for example, the lead could be flowedthrough the mould 12 or it could be sucked back to enhance run back.

The apparatus and method have substantially been described in connectionwhere the bush is substantially flush with the lid. As has already beenindicated, the apparatus and method will also work where the bush is ofthe same height as the intended terminal, but in that case the amount oflead being utilised on each operation will be small, as it will only befilling in deficiencies in the upper surface of the fused post and bushassembly. This is however an important usage of the apparatus andmethod, because many manufacturers have significant problems inachieving a suitable surface finish in that case.

1. Apparatus for forming a terminal on a battery, wherein the battery has a lid having a metal bush and a post connecting a group within the battery and located with its free end in the bush including: (a) a fusing device for fusing the post to the bush to form an assembly, (b) a mould having a cavity receiving the assembly and for forming or finishing a terminal characterised in that the mould cavity extends above the intended height of the terminal to allow for overfilling of the mould and the cavity includes a constant height structure to define the final fill level of the mould.
 2. Apparatus as claimed in claim 1 further including a pump for pumping molten material into the cavity.
 3. Apparatus as claimed in claim 1 wherein the molten material is introduced into the mould via the constant height structure.
 4. Apparatus as claimed in claim 3 wherein the constant height structure is in communication with an inlet/outlet channel.
 5. Apparatus as claimed in claim 4 wherein the inlet/outlet channel includes a valve for determining the height of molten material in the inlet/outlet channel relative to the constant height structure.
 6. Apparatus as claimed in claim 1 wherein the constant height structure is a weir.
 7. Apparatus as claimed in claim 6 wherein the weir is inclined downwardly in the direction of outflow from the cavity.
 8. Apparatus as claimed in claim 1 further including a displacement body for introduction into the mould cavity to ensure that any excess material flows out of the mould.
 9. Apparatus as claimed in claim 1 wherein the fusing device is a heatable probe for engaging and fusing the post and bush.
 10. Apparatus as claimed in claim 9 wherein the tip of the probe is formed to engage the tip of the post.
 11. Apparatus as claimed in claim 9 wherein the probe has a dependent skirt at its tip for melting at least part of the inner periphery of the bush.
 12. Apparatus as claimed in claim 9 wherein the probe is mounted for movement into and out of the mould cavity.
 13. Apparatus as claimed in claim 12 above dependent on claim 8 wherein the probe constitutes the displacement body.
 14. Apparatus as claimed in claim 9 wherein the probe is heated by at least one gas jet.
 15. Apparatus as claimed in claim 14 further including a control for increasing the strength of the gas jet when the probe is remote from the cavity after moulding to surface treat the tip of the terminal and/or to displace any flashings from the terminal.
 16. Apparatus as claimed in claim 1 wherein a part of the mould includes a thermal break adjacent the level of the lid of the box to retain heat at the base of the mould.
 17. A method for forming a terminal on a battery wherein the battery has a lid having a metal bush and a post connected to a group within the battery and located with its free end in the bush wherein the post is initially fused to the bush and the terminal is moulded on the fused bush and post assembly in a mould encircling the assembly characterised in that the mould is initially overfilled with terminal forming material and subsequently the excess material is allowed to flow out of the mould.
 18. A method as claimed in claim 17 wherein the post is fused to the bush whilst located in the mould.
 19. A method as claimed in claim 18 wherein the post and bush are fused by engagement by a heated probe introduced into the cavity of the mould.
 20. A method as claimed in claim 18 wherein the probe is withdrawn from the cavity during filling of the mould and subsequently dipped into the mould cavity to displace any remaining excess material.
 21. A method as claimed in claim 17 wherein a jet of hot gas is played on the surface of the terminal, after the excess material has flowed out, to remove any flashings.
 22. A method as claimed in claim 17 wherein heat is retained in area of the assembly whilst the terminal solidifies.
 23. A method as claimed in claim 17 wherein the tip of the terminal is re-heated as solidification occurs. 